Personal loans take money before promised date

So FNB personal loans sent me an sms on 25 November 2019 stating that my December debit will be deducted as soon as my salary goes in, I was ok with that. Today 13 December 2019;I get an sms saying "FNB:) Dear MR T VEERASAMY. To keep your Personal Loan account up to date and give you peace of mind, your debit order was processed today."

Who gives yourll the right to go into my account and take my last money in my account. I don't know when I will get paid in December and I need money to live till I get paid yourll just go in and take my money. No communication that yourll will take it earlier than the last communication. I need to fill petrol and live till I get paid. This is so not on. Now I'm left with no money in my account. Fnb pathetic!!